scholarly journals The Roles of Riboflavin and Inhibitors in Conidial Germination in Peronospora Tabacina Adam

1966 ◽  
Vol 19 (2) ◽  
pp. 335 ◽  
Author(s):  
CJ Shepherd ◽  
I Tosic
Keyword(s):  
Spore Germination ◽  
Leaf Surface ◽  
Conidial Germination ◽  
Water Soluble ◽  
Natural Conditions ◽  
Peronospora Tabacina ◽  
Tobacco Leaves ◽  
Washing Process ◽  
Good Germination ◽  
Exogenous Source

Shepherd (1962) reported results suggesting that conidia of Peronospora tabacina Adam required an exogenous source of riboflavin for germination, but noted that the technique used was open to the objection that material might be leached from the spores during the washing process. Washing was found to be obligatory by Shepherd and Mandryk (1962) in order to obtain good germination and it was suggested that conidia contained a water-soluble auto-inhibitor of germination. Subsequently, Shepherd and Mandryk (1963) showed that washing removed materials inhibitory to spore germination from the surfaces of tobacco leaves. It was of interest, therefore, to determine whether the postulated auto-inhibitory materials were, in fact, picked up from the leaf surface during spore removal or were endogenous to conidia and also to examine further the riboflavin requirement of conidia removed from the leaf under more natural conditions than were used previously.

scholarly journals Antagonism of Bacillus thuringiensis to phytopathogenic micromicetes as pathogens of apple trees

2021 ◽  
Author(s):  
О. Sherstoboeva ◽  
А. Krzyhanivsky ◽  
А. Bunas
Keyword(s):  
Bacillus Thuringiensis ◽  
Nutrient Medium ◽  
Leaf Surface ◽  
Water Soluble ◽  
Ecological Niches ◽  
Negative Consequences ◽  
Apple Trees ◽  
Produce Water ◽  
Antagonistic Microorganisms

Antagonistic microorganisms, producing bactericidal and fungicidal substances, spread in space and occupy various ecological niches. Antagonistic action of microorganisms can be combined with a number of other properties that can be used by humans for their own purposes. Microorganisms — agents of biological products often have a multifunctional effect on the components of the agroecosystem, which under the influence of various environmental factors could have positive and negative consequences. The aim of the study was to study the effect of new highly active entomopathogenic strains of Bacillus thuringiensis on non-target objects — components of the biocenosis of the apple orchard. When developing technologies for biocontrol of the number of apple trees pests using B. thuringiensis revealed an additional positive protective effect — reducing the number of pathogens of fungal diseases on the leaf surface. Treatment of apple leaves with a liquid culture of strain B. thuringiensis 0376 after 72 hours of application reduced the number of scab of Fusicladium dendriticum by 7 times, and the pathogen of monolisis of Monilia fructigena — 9 times. Strain B. thuringiensis 0371 showed the highest level of antagonism, because in vitro completely inhibited the growth and development of micromycetes on the surface of the nutrient medium. On the leaf surface, the application of culture strain 0371 reduced the number of Fusicladium dendriticum by 92%, and Monilia fructigena — by 86% after 72 hours of treatment. In a field experiment when treating apple trees with a culture of this strain, scab development decreased by 7.1%. Strain B. thuringiensis 787 did not show antagonism against phytopathogenicmicromycetes during co-cultivation on nutrient medium, which may be explained by its inability to produce water-soluble exotoxin, in contrast to strains of B. thuringiensis, which are antagonists of scab and apple monolisis. Strain B. thuringiensis 0371 requires further research and development of its formulations, because it is promising for the creation of a complex biological product with insect-fungicidal properties for use in ecological and agriculture friendly technologies.

scholarly journals Colonization and movement of GFP-labeled Clavibacter nebraskensis in maize

Plant Disease ◽  
2020 ◽  
Author(s):  
Alexander Mullens ◽  
Tiffany Jamann
Keyword(s):  
Crop Residue ◽  
Fluorescent Protein ◽  
Control Method ◽  
Leaf Surface ◽  
Leaf Tissue ◽  
Primary Control ◽  
Bacterial Strains ◽  
Natural Conditions ◽  
Disease Symptoms ◽  
Green Fluorescent

Clavibacter nebraskensis (Cn) causes Goss’s bacterial wilt and leaf blight, a major disease of maize. Infected crop residue is the primary inoculum source and infection can occur via wounds or natural openings, such as stomata or hydathodes. The use of resistant hybrids is the primary control method for Goss’s wilt. In this study, colonization and movement patterns of Cn during infection were examined using green fluorescent protein (GFP)-labeled bacterial strains. We successfully introduced a plasmid to Cn via electroporation, which resulted in GFP accumulation. Fluorescence microscopy revealed that in the absence of wounding, bacteria colonize leaf tissue via entry through the hydathodes when guttation droplets are present. Stomatal penetration was not observed under natural conditions. Bacteria initially colonize the xylem and subsequently the mesophyll, which creates the freckles that are characteristic of the disease. Bacteria infiltrated into the mesophyll did not cause disease symptoms, could not enter the vasculature, and did not spread from the initial inoculation point. Bacteria were observed exuding through stomata onto the leaf surface, resulting in the characteristic sheen of diseased leaves. Resistant maize lines exhibited decreased bacterial spread in the vasculature and the mesophyll. These tools to examine Cn movement offer opportunities and new insights into the pathogenesis process and can form the basis for improved Goss’s wilt management through host resistance.

scholarly journals Resistance to Boscalid Fungicide in Alternaria alternata Isolates from Pistachio in California

Plant Disease ◽  
2007 ◽  
Vol 91 (10) ◽  
pp. 1345-1350 ◽  
Author(s):  
Herve F. Avenot ◽  
Themis J. Michailides
Keyword(s):  
Spore Germination ◽  
Alternaria Alternata ◽  
Hyphal Growth ◽  
Conidial Germination ◽  
Prior History ◽  
In Vitro Tests ◽  
Fitness Parameters ◽  
History Of ◽  
The Mean

Boscalid is a new carboxamide fungicide recently introduced in a mixture with pyraclostrobin in the product Pristine for the control of Alternaria late blight of pistachio. In all, 108 isolates of Alternaria alternata were collected from pistachio orchards with (59 isolates) and without (49 isolates) prior exposure to boscalid. The sensitivity to boscalid was determined in conidial germination assays. The majority of isolates from two orchards without a prior history of boscalid usage had effective fungicide concentration to inhibit 50% of spore germination (EC50) values ranging from 0.089 to 3.435 μg/ml, and the mean EC50 was 1.515 μg/ml. Out of 59 isolates collected from an orchard with a history of boscalid usage, 52 isolates had EC50 values ranging from 0.055 to 4.222 μg/ml, and the mean EC50 was 1.214 μg/ml. However, in vitro tests for conidial germination and mycelial growth also revealed that seven A. alternata isolates, originating from the orchard exposed to boscalid were highly resistant (EC50 > 100 μg/ml) to this fungicide. Furthermore, in vitro tests showed no significant differences between wild-type and boscalid-resistant mutants in some fitness parameters such as spore germination, hyphal growth, sporulation, or virulence on pistachio leaves. Experiments on the stability of the boscalid-resistant phenotype showed no reduction of the resistance after the mutants were grown on fungicide-free medium. Preventative applications of a commercial formulation of boscalid (Endura) at a concentration which is effective against naturally sensitive isolates failed to control disease caused by the boscalid-resistant isolates in laboratory tests. To our knowledge, this is first report of field isolates of fungi resistant to boscalid.

THE RELATION BETWEEN DEW AND TOBACCO WEATHER FLECK

1966 ◽  
Vol 46 (4) ◽  
pp. 349-353 ◽  
Author(s):  
F. D. H. Macdowall
Keyword(s):  
Oxygen Uptake ◽  
Causal Relationship ◽  
Leaf Surface ◽  
Tobacco Leaves

The coincidence of dew and fleck in tobacco leaves has suggested a causal relationship. However, water condensed on the leaf surface or temporarily infiltrated into areas of lamina did not cause any visible damage to the tissues and did not contribute to the amount of fleck caused by a preceding dose of ozone. In fact, infiltrated water delayed the development of fleck symptoms caused by ozone, by suppressing damaging rates of oxygen uptake.

The superhydrophilic and superoleophilic leaf surface of Ruellia devosiana (Acanthaceae): a biological model for spreading of water and oil on surfaces

2009 ◽  
Vol 36 (4) ◽  
pp. 339 ◽  
Author(s):  
Kerstin Koch ◽  
Inga Christina Blecher ◽  
Gabriele König ◽  
Stefan Kehraus ◽  
Wilhelm Barthlott
Keyword(s):  
Leaf Surface ◽  
Cell Types ◽  
Water Soluble ◽  
Tween 20 ◽  
Environmental Scanning ◽  
Leaf Surfaces ◽  
Zero Degree ◽  
Water Soluble Extract ◽  
Growing Conditions ◽  
Different Cell Types

Most leaves of plants are hydrophobic or even superhydrophobic. Surprisingly the leaves of the tropical herb of Ruellia devosiana Makoy ex E. Morr. Hort. (Acanthaceae) are superamphiphilic. Water droplets (10 µL) spread to a film with a contact angle of zero degree within less than 0.3 s. Such surfaces with a high affinity to water are termed superhydrophilic. Droplets of oil applied on R. devosiana leaves and replicas showed a similar spreading behaviour as water. These surfaces are superoleophilic, and in combination with their superhydrophilicity they are called superamphiphilic. Independent of the growing conditions, a reversibility of the superhydrophilicity in R. devosiana leaves was found. Additionally, on 90° tilted leaves a pressure free capillary transport of water occurs against the force of gravity. By using a low pressure environmental scanning electron microscope (ESEM), the water condensation and evaporation process on the leaves has been observed. The leaf surfaces are composed of five different cell types: conical cells, glands, multicellular hairs, hair-papilla cells and longitudinal expanded, flat epidermis cells, which, in combination with the surrounding papilla cells, form channel like structures. Replication of the leaf surface structure and coating of the replicas with hydrophilic Tween 20 and a water soluble extract gained from the leaf surfaces resulted in artificial surfaces with the same fast water spreading properties as described for the leaves.

scholarly journals Nature of Resistance of Pecan Cultivars to Black Pecan Aphids

HortScience ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 441D-441
Author(s):  
Bruce W. Wood ◽  
Charles C. Reilly
Keyword(s):  
Reproductive Success ◽  
Leaf Surface ◽  
Resistance Mechanisms ◽  
Water Soluble ◽  
Chemical Component ◽  
Economic Losses ◽  
Feeding Adaptation

Foliar feeding by the black pecan aphid [Melanocallis caryaefoliae (Davis)] can cause tremendous economic losses. Evaluations of black aphids on pecan genotypes indicates that both antixenosis and antibiosis-like resistance mechanisms exists. Tests for antixenosis indicated that aphids possess clear preferences for certain genotypes over others and that this preference can be dependent on a water-soluble chemical component of the leaf surface. Aphids also exhibited a “conditioning preference,” in which they preferentially feed on genotypes from which they originated. Antibiosis tests indicated that pecan genotypes influence the reproductive success of aphids already possessing a feeding adaptation to those same pecan genotypes; therefore, an evaluation of 30 cultivars for antibiosis indicated that populations developed only 20% as fast on `Choctaw' and `Alley' as on `Desirable' and `Success'. No cultivar was observed to essentially prevent aphid reproduction.

scholarly journals Ethnomodelling on atag construction in Ajung Village, Jember Regency

2021 ◽  
Vol 6 (1) ◽  
pp. 129-138
Author(s):  
Yusfan Adeputera Yusran ◽  
Sri Utami ◽  
Surjono ◽  
Atsar Yaisy Muhammad
Keyword(s):  
Curing Process ◽  
Natural Conditions ◽  
Technical Aspects ◽  
Tobacco Leaves ◽  
Local Materials

Atag functions as a place for the air curing process to dry tobacco leaves. This building, which is made of bamboo, has existed in Indonesia since 1850 and used to produce authentic quality cigars. Initially, this building was only utilized for local materials, however, based on the shape, dimensions, and construction, there is a tendency for atag to be established by considering several technical aspects. Therefore, this study aims to examine the technical ideas, such as calculations, practices, and procedures for making Atag using the ethnomodelling strategy. The results showed that the community's practices and calculations in building atag were a logical response in adapting to natural conditions such as climate, wind, and humidity. It also provided intelligence in utilizing the potential of local materials such as bamboo and sugarcane leaves

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